function [ ] = mx_eyelink_command_result( )
%MX_EYELINK_COMMAND_RESULT Check for and retrieves the numeric result code sent
% by the tracker from the last command.
%
% Returns:
% NO_REPLY if no reply to last command.
% OK_RESULT (0) if OK.
% Other error codes represent tracker execution error.
%
%----------------------------------------------------------------------------
% Copyright Eduardo Aponte 2013
% aponteeduardo@gmail.com